If those numbers happen to be on a 25 watt guitar amp with reverb, then they mean something, if they are on another amp they are probably just a model number assigned to the unit by whoever made it. There doesn't seem to be a standard series of abbreviations but a few fairly common ones are.... "R" often means the unit has reverb, "X" is used to indicate the unit has built in effects, "DX" for digital effects, "G" for guitar amp, "B" for bass amp, "C" for chorus. These and others are used and seem fairly obvious, sometimes model numbers have nothing to do with an amp's ratings.